WO2000042693A1

WO2000042693A1 - Device and method for distribution of uninterruptible electric power

Info

Publication number: WO2000042693A1
Application number: PCT/SE2000/000082
Authority: WO
Inventors: John ÅKERLUND; Anders Larsson
Original assignee: Telia Ab
Priority date: 1999-01-18
Filing date: 2000-01-17
Publication date: 2000-07-20
Also published as: SE517112C2; AU2337600A; SE9900126D0; SE9900126L

Abstract

The present invention relates to a device and method for uninterruptible power supply. An ordinary AC voltage source, p, supplies an AC voltage to a converter, L, which conveys a DC voltage to voltage converters, S. The voltage converters, S, adapt the received DC voltage to one for the users adapted DC voltage, or conversion to one by the users adapted AC voltage. In connection to the converter, A, a DC voltage is arranged adapted to bridge a time corresponding to the connection and start up time for a standby electrical power unit, G. The suggested solution makes possible that standby electric power is offered without interruption.

Description

DEVICE AND METHOD FOR DISTRIBUTION OF UNINTERRUPTIBLE ELECTRIC POWER

FIELD OF THE INVENTION The present invention relates to distribution of electric power from a supplier to a consumer. The intention is to create an uninterruptible supply of electric power to functionalities that should not be discontinued at power failure/interruption in the ordinary supply of electric power. The invention is primarily intended for telecommunication equipments, alarm equipments etc, which traditionally are expected to function also at power failure/interruption in the ordinary electric power mains.

PRIOR ART

Suppliers of electric power mainly distribute alternating voltages to consumers of electric power. For certain users, such as telecommunication operators, hospitals etc, this standby electric power has been arranged locally. This standby electric power has been supplied by batteries, or by locally arranged diesel-powered electric generators. At power failures/interruptions of longer duration, telecommunication operators, for instance, have been forced to arrange standby electric power by transport of, for instance, diesel-powered standby electric power units to telecommunication exchanges that have lost their main power source. These measures must be taken if the electric power failure/interruption is expected to exceed the capacity of the batteries. Patent application No PCT/SE98/01611 is an example, where the problem of standby electric power is illuminated.

TECHNICAL PROBLEM

Society of today tends to be more and more vulnerable and depending on electric power supply without interruption. A field that is expected to function independent of the public electric power supply are the telecommunications. The standby electric power units that are utilised at larger, centrally located, telecommunication exchanges are in many cases motorpowered. These standby electric power units are started at interruption in the supply of public electric power. In order to overlap the time that is passing before the standby power unit reaches full effect, batteries are utilised, which supply electricity, at which loss of important data and information and communications in progress does not ensue.

In the society of today, the dependence on functioning telecommunications tend to increase, as will the expectation that they shall function, even if other functions fail. The traditional telephones have been independent of the function of the electric power network in the sense that they have had sufficient capacity to function at least for a day or some 24 hours, without any special measures having been necessary to take. The telecommunication equipments of today to a greater and greater extent require that supply of electric power be taken from the ordinary electric mains instead of from the telecommunications network. This also apply to mobile telephones and their base stations that obtain charge of their batteries via specific charging equipments that are connected to the mains. In order to bridge these problems, there are wishes to provide electric power systems that are redundant, but only offer a limited power. Besides telecommunication systems, for instance alarm systems of different kinds, security systems, supervisory systems etc, need reliable supply of electric power. Traditionally, batteries are utilised locally at telecommunication exchanges and telecommunication equipment located at the subscriber^'s. These systems include larger or smaller batteries, which provide standby times from minutes up to hours. A disadvantage of batteries is that these have to be maintained and that they constitute a load on the environment. Further, there is a great risk that the batteries are not in good condition when their assistance is needed. To utilise standby electric power units is a possibility to extend the time of operation at power failure/interruption. Also these systems are expensive and in certain cases cannot without great difficulties be connected to the telecommunication exchanges. Telecommunications administrations in the world have a number of motorpowered electric power plants connected in cities and in other strategic places in respective countries. Since these electric power plants have been dimensioned with regard to older mechanical telecommunication systems, the electric power plants have a capacity that heavily exceeds the requirements of the telecommunication systems of today. This surplus capacity might be utilised, at least to a limited extent, to offer electricity for other purposes.

Traditional transmission and distribution of electric power with comparatively low power is made by 3- or 1-phase and by alternating voltage (AC voltage) . In these systems, the powers are difficult to control, limit and balance, so that the distribution is stable and with high electric quality. Problems of load bias further occur in the feeding 3-phase system at 1-phase distribution. At utilisation of high alternating voltage in cables for transmission over long distances, stability problems will occur as a consequence of capacitive voltage increase. In order to bridge the above mentioned problems, the public electric power networks/telecommunication networks should be supplemented with one at least partly redundant electric power network with built in uninterruptible standby power (UPS) , which makes possible that uninterruptible electric power can be transferred and delivered to the houses of the customers. Discussions regarding the possibility to provide a more reliable electric power, premium power, to the subscribers, at, for instance, an increased price, have been carried on. How this supply shall be arranged has so far not been shown. Such wishes are met with at private persons, companies and public institutions.

The present invention has the intention to solve the above mentioned problems.

THE SOLUTION

The present invention relates to a device and method at distribution of electric power for creation of uninterruptible supply of electric power. An electric power source, p, supplies preferably an alternating voltage, which is converted to preferably a direct voltage in a converter, A. In, or in connection to, the A-converter, a DC voltage source, L, is arranged. At interruption in the supply of electric power from the electric power source, p, the DC voltage source, L, voltage feeds the system during a period of time that is needed before an alternative AC voltage source, for instance a generator, G, is started/connected and takes over the voltage feed. The supply of electric power is in this way executed without voltage interruption. The DC voltage source, L, consists for instance of accumulators and/or super capacitors. The supply of electric power from the DC voltage source is arranged to voltage feed the system during the period of time that will pass before the alternative voltage source, G, is connected/switched on/ started. The DC voltage source is connected to the input/output of the converter, A and/or S, or in the converter. The DC voltage source further provides a voltage corresponding to the from the electric power source, p, supplied peak value of the AC voltage. At planning at S, the DC voltage source supplies the peak value, or root- mean-square value, of the AC voltage. Converter, A, and/or voltage converter, S, are arranged to limit the power drain at user, a. Control equipments, T, are arranged in, or in connection to, the converters, A, and/or the voltage converters, S, and control A and S so that G will not be overloaded.

The alternative voltage source, G, includes one or more, preferably parallel connected AC voltage sources, which together supply a sufficient power, so that, a, has redundancy. Converters A and S include one or more preferably parallel connected units, so that A and S have redundancy. A and G, or their sub units, also can be arranged so integrated that they are connected to each other, and parallel connection only is made at the DC voltage side. The AC voltage sources are allowed to be connected and disconnected according to the actual need of power. The connection and disconnection is made with regard to information collected by the control equipments, T. The local voltage converters, S convert the received DC voltage to one for the users adapted DC voltage. There also can be conversions to AC voltage in the cases when need exists. The invention further relates to a method for distribution of uninterruptible electric power. A voltage source, p, G, supplies a voltage, and a DC voltage source, L, supplies a DC voltage. A converter is fed, depending on the value of the voltage respective DC voltage, by either the voltage or the DC voltage. The converter, A, supplies an output voltage to other converters, S, and/or users, a. The other converters, S, have corresponding function as the converter, A. The converters, A, further include a circuit, C, which at the input side, is fed by the DC voltage/voltage and at the output side, U, the output voltage is obtained. The DC voltage, DC, is selected to a value corresponding to the peak value of the voltage AC/DC. The output voltage is allowed to be a DC or AC voltage, which is adapted and power limited depending on existing needs. The from the converter, A, obtained output voltage consists of a high voltage, which is converted to one for the users usable voltage in the converters, S. Control equipments, T, in the converters, A, S, limit the power drain to the converters, S, to respective the users, a . At electric power failure/interruption from the voltage source, p, the DC voltage source, L, takes over the electric power supply during a period of time necessary for connection/start up of an alternative voltage source, G. The voltage sources, p, G, are allowed to be AC or DC voltage sources. Users, a, connect themselves to electric power points/sockets, E, which power points/sockets E, are equipped with, for instance, electronic power supervision and power limiting electronics, which automatically switches off the electric current to the user, a, if a predetermined or processable maximal power/current drain is exceeded. Programming can be made, for instance, remotely or by so called smart card.

ADVANTAGES The suggested solution has the advantage that electric power distribution from different sources is facilitated. Further, both AC and DC voltage sources can be connected to one and the same system without causing any conflicts. Existing standby power units, which have been dimensioned for higher power needs than the technology of today require, can in this way offer, at least to a limited number of users, uninterruptible electric power supply. Users in this way can be offered what is called "premium electric power" , that is that subscribers to electric power for an additional fee can be allocated a certain electric power, which can be utilised also at failure of/interruption in ordinary electric power supply. The change between the distribution of electric power between the AC voltage source and the DC voltage source is made, at the user, further without interruption because relays, connectors etc are not needed, as can be seen in Figure 2. By this solution is made possible that the period of time for change to other AC voltage source, or motorpowered power supply, can be bridged, by means of, preferably small, batteries or capacitors, for instance so called super capacitors .

The utilised circuit according to Figure 2 makes possible that DC voltage power is fed out from the device, alternatively AC voltage by additional circuits at the output stage. The output voltage levels from the device are adapted according to current need and comprise all voltage levels and powers. The invention makes possible that rectified high voltage can be produced and supplied to subscribers and, if needed, be converted to AC voltage in/at the subscriber' s equipment, alternatively in converter for specific subscriber, area etc.

Another advantage is that generators, transformers etc, can be equally loaded, irrespective of the load of the network by the users. Further, there will be no problems to balance the powers, control or stability problems. Local connection of P near a, gives redundancy to a, via the circuit C. By Figure 3 is shown diagrammatically how a user, a, obtains current via ordinary electric power suppliers, R. These suppliers, R, distribute electric power at least to some extent/some parts over one and the same line/cable. This results in that a line breakdown leads to that the subscriber, a, at these occasions will completely lose the supply of electric power. By the invention is suggested that electric power is distributed an alternative route from p that also has access to standby power sources according to the invention. The electric power supply from p and R can, according to the invention, be arranged in the same power point/socket, or in different power points/sockets, without the systems causing problems for each other. BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 shows the principle of the invention.

Figure 2 shows a rectifier circuit that is utilised in the invention.

DETAILED DESCRIPTION OF AN EMBODIMENT OF THE INVENTION

In the following, invention is described with reference to the figures and in them given terms.

The present invention relates to a device for uninterruptible supply of electric power. An ordinary/regular AC voltage source/DC voltage source, p, supplies a voltage to a converter, A, which transfers a DC voltage/AC voltage to voltage converters, S. The voltage converters, S, adapt the received DC voltage/AC voltage to one for the users adapted DC voltage, or conversion to one for the users adapted AC voltage. In connection to the converter, A, a voltage source, L, is arranged, adapted to bridge a time corresponding to the connection/start-up time for a standby electric power unit, G. The voltage source, L, takes its power from a storing media, for instance battery, capacitor, flywheel etc, and the voltage is allowed to be both DC and AC voltage, depending on selected storing media. The suggested solution makes it possible to offer standby electric power without interruption of current.

In Figure 2 is shown the principle for current feed in the described invention. This rectifier circuit/inverter circuit is used in A and for current feed of among other things computers, low-energy lamps, home electronics etc. The advantage of the shown circuit is that it can be utilised for connection to both AC and DC voltage sources. The AC voltage source/DC voltage source, AC, respective the DC voltage source, DC, are connected parallel to the rectifier circuit. The DC voltage, DC, is selected to a value that corrresponds to the peak value of the AC voltage/DC voltage, AC/DC. The DC voltage source can be batteries, accumulators, capacitors etc, depending on the need of capacity at loss of the AC voltage/DC voltage, AC /DC. In operation, that one of the voltage sources that has the highest voltage will feed the rectifier circuit, C. The change between the voltage source, AC/DC, and the DC voltage source, L, and vice versa, is made quite without interruption, so the equipments that have been connected to the rectifier circuit, C, are not influenced by the change. The on the secondary side produced voltage is adapted to voltages and powers corresponding to the current needs.

Consequently, low voltages, one or a few volts, up to high voltages, hundreds or thousands of volts, can be produced in the described rectifier circuit. Both AC voltage and DC voltage can be produced on the secondary side of the converter, A, and/or the converters, S. Other circuits than the in Figure 2 shown circuit may exist or will turn up in the future. These other circuits can be utilised in the present invention and produce the same power. In normal operation, an AC voltage/DC voltage is obtained from a supplier of electric power, p. The AC voltage/DC voltage is received in a converter, A, from where a DC voltage/AC voltage is distributed to users, a. The distributed DC voltage/AC voltage is converted to one for the users suitable voltage in voltage converter, S. The conversion in the first place refers to from DC voltage to DC voltage, but nothing prevents that the conversion is made to an AC voltage directly in the converter, or via one for the purpose selected converter. The selection is of course depending on the user's needs and wishes. Control equipments are further arranged in connection to the converter, A, and/or in connection to the voltage converters, S. The control equipment/equipments supervise the power drain and takes measures in case that the power drain exceeds one in advance decided maximal power. The measures are allowed to vary depending on the situation and the degree of importance. The power points/sockets, E, feed users, a. E are power limiting power points/sockets, which have programmable output power and can switch off the current to a, if the power drain exceeds what is allowed. E can have communication with T, but is aslo allowed to be locally programmed by, for instance, smart card. The users are categorised, for instance, according to the priority the user has been allocated. For instance are functions important to society allocated a high priority, as well are vital functions, whereas other functions are given a priority according to a falling scale. In a corresponding way, different functions with a user are allocated different priorities depending on their importance for the user^'s needs. The control equipment/equipments is/are given information about different functionalities related to the equipments of the users, and allowed power drains. At risk of overloading, or on occasions where the power in the feeding network is not sufficient, the power is switched off, or limited, in parts of the user's equipment. The centrally located control equipments can control the users current drain individually; the current drain in parts of the electric power network according to present needs, and according to allocated electric powers.

In, or in connection to, the converter, A, a DC voltage source, L, is connected. Further, there are one or more AC voltage sources, G, the task of which is to take over production of electricity when the ordinary voltage source, p, stops supplying electricity. The AC voltage sources, G, consist of voltages distributed over alternative paths and by independent producers of electric power, for instance different suppliers, the same supplier with electric power distribution via separate paths and from each other independent production of electric power. Locally, the electric power further can be produced m motorpowered electric power plants. These alternative electric power productions shall, however, be connected and/or started up before the electric power distribution again is functioning. Depending on the capacity of the electric power source, the capacity can, in such a case when the standby electric power source is connected, be lower than in normal operation. The control equipments, T, have in this state to control the allocation of electric power between the users according to needs and decided priorities .

At a failure of/interruption in the power supplies from the ordinary voltage source, p, the DC voltage source will immediately supply a DC voltage. The supply of the DC voltage is arranged separately at the input of the converter, in the converter, or at the output side of the converter. The DC voltage source consists of systems that accumulate electric power, for instance accumulators, capacitors etc. Selection of DC voltage source is decided with regard to the need of power that exists, and the time that is calculated to pass before the alternative voltage source, G, has been connected and/or started up. In the case that capacitors are used, so called super capacitors are preferably utilised. The DC voltage source is kept loaded during normal operation by devices that are well known both to the layman and the expert. The voltage of the DC voltage feed is selected to correspond to the peak value of the feeding AC voltage source. There is, however, nothing to prevent utilisation of other voltages. The selection is made depending on the actual need in the individual case. The location of the voltage source, L, is allowed to be made at for the purpose suitable place in the system. The electric power distribution refers in the first place to DC voltage to the user equipments. This is possible and favourable in that a lot of equipments, such as computers and other equipments, convert the normally received AC voltage to DC voltage. These equipments normally function with both DC and AC voltage. Risks of shorter or longer interruptions in the supply of electric power are further minimised because the DC voltage source immediately takes over the voltage feed, at interruption in the ordinary voltage supply, until the alternative voltage source is in use.

The suggested solution further has the advantage that bias in loading of the p and/or G of the AC voltage source does not occur.

The invention is not limited to what has been described above, or in the following patent claims, but can be subject to modifications within the frame of the idea of invention .

Claims

PATENT CLAIMS

1. Device for distribution of uninterruptible electric power, at which a voltage is supplied from an electric power source (p) , which voltage is converted to a DC voltage/AC voltage in a converter (A) , c h a r a c t e r i s e d in, that a DC voltage source (L) is arranged in, or in connection to, the converter (A) and at interruption of the supply of electric power from the power source (p) , the DC voltage source during a limited period of time is arranged to voltage feed the converter (A) , until an alternative voltage source (G) is started up/connected and takes over the distribution of electri power, at which the distribution of electric power is made without interruption .

2. Device, as claimed in patent claim 1, c h a r a c t e r i s e d in, that the DC voltage source (L) consists of, for instance, an accumulator, or at least a super capacitor, at which the DC voltage source is arranged to supply the electric power during a period of time sufficient to connect/switch on an alternative voltage source (G) .

3. Device, as claimed in patent claim 1, or 2, c h a r a c t e r i s e d in, that the DC voltage source (L) is arranged to take over the supply of electric power during periods of time corresponding to parts of hours, preferably minutes.

4. Device, as claimed in patent claim 1, 2 or 3, c h a r a c t e r i s e d in, that the DC voltage source is arranged to be connected to the input of the converter.

5. Device, as claimed in any of the previous patent claims, c h a r a c t e r i s e d in, that the alternative voltage source (G) is arranged to be part of the converter (A) .

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6. Device, as claimed in any of the previous patent claims, c h a r a c t e r i s e d in, that the DC voltage source (L) is arranged in, or in connection to, the converter (A) . 0

7. Device, as claimed in any of the previous patent claims, c h a r a c t e r i s e d in, that the DC voltage source is arranged to supply a voltage corresponding to the peak voltage of the voltage 5 source (p, G) .

8. Device, as claimed in any of the previous patent claims, c h a r a c t e r i s e d in, that a circuit according to Figure 2 is utilised, at which the DC 0 voltage (DC), respective the voltage (AC) are at the same time connected to the circuit, that the one of the voltage sources that supplies the for the moment highest voltage feeds the circuit, and that change between the voltage sources (AC/DC) is made without 5 voltage interruption.

9. Device, as claimed in any of the previous patent claims, c h a r a c t e r i s e d in, that the converter (A) and/or local voltage converters (S) are 0 arranged to limit the power drain at the user (a) , respective that the converters (A, S) and /or power points/sockets (E) at the users are controlled by, for instance, a smart card.

10. Device, as claimed m any of the previous patent claims, c h a r a c t e r i s e d in that control equipments (T) are arranged m, or close to, the converters (A, S) .

11. Device, as claimed in any of the previous patent claims, c h a r a c t e r i s e d in, that the alternative voltage source (G) is arranged to include a number of parallel connected voltage sources, which individually or together are arranged to distribute one for the electric power distribution sufficient power .

12. Device, as claimed in patent claim 11, c h a r a c t e r i s e d in, that the in the voltage source (G) parallel arranged voltage sources (G) are arranged to be connected/disconnected depending on a need of power that exists at the moment.

13. Device, as claimed in any of the previous patent claims, c h a r a c t e r i s e d in, that the local voltage converters (S) are arranged to convert the received voltage to one for the receiver suitable voltage .

14. Device, as claimed m patent claim 13, c h a r a c t e r i s e d in that the converted voltage is allowed to be DC or AC voltage, and that the voltage sources (p, G) are arranged to be AC voltage sources and/or DC voltage sources, and that the power drain in the power points/sockets (E) is arranged to be limited or to be disconnected, at which power limiters and disconnecting programmable functions are arranged to be remotely controlled, or by, for instance, a smart card.

15. Method, for distribution of uninterruptible electric power, at which a voltage source (p, G) supplies a voltage, and a DC voltage source (L) supplies a DC voltage to a converter (A) , c h a r a c t e r i s e d in, that the converter (A) , depending on the value of the voltage respective DC voltage, is voltage fed by either the voltage or the DC voltage, that from the converter (A) is obtained an output voltage that is distributed to other converters (S) and/or users (a) .

16. Method, as claimed in patent claim 15, c h a r a c t e r i s e d in, that other converters (S) have the same functionalities as the converters (A) .

17. Method, as claimed in patent claim 15, or 16, c h a r a c t e r i s e d in, that the converters (A, S) include a circuit (C) , which at the input side obtains the DC voltage respective the voltage, and that on the output side (U) is obtained the output voltage .

18. Method, as claimed in any of the patent claims 15-17, c h a r a c t e r i s e d in, that the voltage (AC/DC) respective the DC voltage (DC) , are connected to the input side of the circuit (C) , at which the DC voltage (DC) is selected to a value corresponding to the peak value of the voltage.

19. Method, as claimed in any of the patent claims 15-18, c h a r a c t e r i s e d in, that at the output side (U) of the circuit (C) , is obtained a voltage that is allowed to be an AC voltage or a DC voltage, which voltage is adapted to a given need, and that the voltage is power limited.

20. Method, as claimed in any of the patent claims 15-19, c h a r a c t e r i s e d in, that at the output side from the converter (A) is obtained high a voltage, which in the other converters are converted to one for user (a) adapted voltage.

21. Method, as claimed in any of the patent claims 15-20, c h a r a c t e r i s e d in, that control equipment (T) are arranged in, or in connection to, the converters (A) , which control equipments (T) limit the power drains to the converters (S) , respective the users (a) , and/or that so called smart cards are utilised for control of the power drain in the users (a) power points/sockets (E) .

22. Method as claimed in any of the patent claims 15-21, c h a r a c t e r i s e d in, that at interruption of the electric power from the voltage source (p) , the DC voltage source (L) takes over the supply of electric power during a period of time that is needed to connect/start up an alternative voltage source (G) .

23. Method, as claimed in any of the patent claims 15-22, c h a r a c t e r i s e d in, that the voltage sources

(p, G) consist of AC and/or DC voltage sources.

24. Device for distribution of uninterruptible electric power, at which an AC voltage is supplied from an electric power source (p) , which AC voltage is converted to a DC voltage in an AC/DC converter (A) , c h a r a c t e r i s e d in, that a DC voltage source (L) is arranged in connection to the AC/DC-converter (A) , and at interruption in the electric power distribution, from the electric power source (p) , the DC voltage source during a limited period of time is arranged to distribute the DC voltage until an alternative AC voltage source (G) is started- up/connected and takes over the distribution of electric power, at which the distribution of electric power is made without interruption.